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DOE 40th Anniversary Milestone: Expansion of Universe is Speeding Up

September 13, 2017

Scientists assumed the universe’s expansion was slowing down as gravity pulled debris from the Big Bang back together. But in 1999 Saul Perlmutter and others discovered the universe’s expansion is speeding up, driven by an unknown cause referred to as “dark energy.” They used measurements from Type 1a supernovae, which all reach maximum brightness when they explode. More>